It's for securing the vehicle to a flat bed tow truck
Here are some pictures on my LX ...
Rear left hand - 51968-60020, LX & LC 2008-2021
Rear right hand - 51095-60020 LX & LC 2008-2021
Front left hand - I'm going to replace the LX retainer with same tow hook as LC and LX right hand hook.
Tow hook 5196060020 (5196060010) LC 2008-2021 - missing on LX so not in the picture. Replaced by "retainer" see below. This is Toyota saving money on a $100k truck, go figure.
Tie down 51963-60060 LX & LC 2008-2021
Retainer 51962-60040 - the hat shaped piece only on LX 2010-2021
Front right hand
Tow hook 5196060020 (5196060010) LX & LC 2008-2021
Tie down 51963-60060 LX & LC 2008-2021
Bolts are the same all around 91672-G1240.
Strange that Toyota designed and installed two different hooks in the rear.
The manual is confusing saying "Do not use the rear emergency towing hook." It does say towing hook. So I think that the right hand rear hook is actually the towing hook not the tie down for securing the truck to the bed. And I think Toyota manual (at least the LX) has an error when they shown the right hand hook instead of the left one. If you try towing from the left one you will indeed do "serious damage to your vehicle" - damage the bumper. Other than that in the worse case it might break the hook but for sure it will not be able to damage the frame.
So if the right hand one is the towing why did Toyota not use the same design as in the front of having the tow hook reinforced by installing the tie down over it. I'm not even sure the tie down hook would fit over inside the rear hook hat. Installing a front tow hook in the rear does not work as the hook will be under the bumper cover that will get damage if hooked.
I do have a hitch shackle for rear towing but I'm still baffled by Toyota design choices for towing points in the rear, especially compared to the front.